genetically as brothers and sisters, or cousins?
2006-12-21 08:01:18 · 6 answers · asked by lowesman4e 1 in Science & Mathematics ➔ Biology
Remember, the sexual cells are haploid, that is, they contain only one half of a set of genes. Among siblings with non-identical parents, you only share about 25% of your genes in common with your brothers and sisters.
Among identical twins, their genes are identical. But still, in this case, you would only share 50% of your genes in common with your siblings. However, given the double identicality of the mated pairs, the cousins would also share 50% of their genes with each other. This assumes that the parents are indeed identical twins, and do not pass on any point mutations, and cross linkages to their offspring.
2006-12-21 09:00:10 · answer #1 · answered by phantomlimb7 6 · 1⤊ 0⤋
On average they would share 1/2 of their genes - making them closer to siblings than cousins. First cousins only share only 1/8 of their genes.
As an aside: to calculate the degree of relatedness between any two individuals, you first count the number of generations separating them. And you count up and down the generations. For example - for myself and my sister - I would count up 1 generation from myself to my parents, then down 1 generation from my parents to my sister. 2 generations. You also need to count the number of shared relatives: in this case 2 because we share both parents (we are full, not half siblings). In sexually reproducing species, 1/2 of genes are passed from each parent to their offspring, so 1/2 is the "magic" number (I won't go on at length about this - too complicated).
So to do the calculation - I take (1/2) and raise it to the power that equals the # of generations I counted. For myself and my sis, this is (1/2)^2= 1/4. Then, multiply by the # of shared relatives (1/4)*(2) = 1/2. I share 1/2 of my genes with her.
This calculation doesn't work for identical twins - because it is designed for 'normal' reproduction. But we know that genetically, identical twins are the same "person." Therefore, the hypothetical offspring of two sets of married identical twins would be equivalent to 'siblings.'
2006-12-21 17:01:16 · answer #2 · answered by panda_glam 2 · 1⤊ 0⤋
Brothers and sisters. Even though the parents (couples) in both cases have the exact same genetic makeup, this does not ensure that their offspring would be completely identical. They would however be like two siblings because the moms are the same, and the dads are the same in each instance.
The events of sexual reproduction, mostly "crossing over" of chromosomes would make them different from each other, however their paternal and maternal backgrounds are the same.
2006-12-21 16:58:08 · answer #3 · answered by Big D 2 · 1⤊ 0⤋
Yes. They might end up looking more like siblings than cousins. It would be as dangerous for them to interbreed as for actual siblings to do so.
Note: When one set of siblings marries another set of siblings, their children are called "double first cousins."
2006-12-21 16:07:07 · answer #4 · answered by Iris 4 · 0⤊ 1⤋
Closer than what? Family? You don't have to be genetically related to have that. Do you???
2006-12-21 16:14:46 · answer #5 · answered by kittyfreek 5 · 1⤊ 0⤋
They would be considered brothers and sisters.
2006-12-21 18:16:38 · answer #6 · answered by mizzbellz 2 · 0⤊ 1⤋